help with D-123

[pos]

here it is:
yellow is 2251J
Oragne is 2251J plus added mass
Red is 251J
all in the same 11L box (14L minus driver displacement, as in the 434X serie)

Pretty accurate indeed
The only strange thing is that in the simulation the 2251J plus added mass has more input under 100Hz than the normal 2251J and 251J.

[Vinnie]

Hi folks
Wanted to report back on how it all turned out as I learned quite a bit and it may be helpful to someone else. I read through all the advice in the posts below, and then I looked at several of jbl's recommendations for different size enclosures for the 123, and I also found a handy site for calculating port size at http://www.carstereo.com/help/Articles.cfm?id=31.
Armed with all this info I decided that the easiest approach was to first try tweaking the existing enclosure (2.5 cf with two 2.25x6.5 ports in the baffle). The jbl info said tune the enclosure to 45hz, so I plugged that and the cf into the port program and put in the size of one port and it said make it 4.6 inches deep. The baffle is 5/8" so I figured an additional 4" would be about right.Made up two of them 2.25 x 6.5 on the inside from 1/2" plywood and glued them to one port in each cabinet. Glued another piece of 1/2" ply over the remaining port in each one. Just for good measure I stuffed each cabinet loosely with poly fiber batting and ran a bead of string caulk under the back cover.
The difference is nothing less than amazing. The bass is very acceptable now, and nice and clean. All the mid range magic is still there too. Not too sure about the high end though, it's tolerable but I wonder if it could be better. Anyone familiar with the University T-202 super tweeter? How good is it supposed to be? Anyone got any recommendations for a replacement tweeter that would match up better with the 123?
Thanks to all who helped earlier, I really appreciate it. It's been fun and educational as well.